The present invention relates to a cooler for an electronic device, for example, a cooler for an electronic device, which is suitable for cooling a CPU, or the like contained in a thin type electronic device such as a notebook personal computer.
Since heating parts are accommodated within an electronic device, it has hitherto been carried out to radiate the heat of the heating parts out of the electronic device so that the heat from the heating parts do not have any adverse influence upon any other electronic parts. In the conventional electronic device, for example, a radiating fin is provided on the upper surface of the heating part to carry out self-cooling via the radiating fin.
However, in a cooler having such a type of a radiating fin as being provided on the upper surface of the heating part in order to carry out self-cooling, the cooler becomes taller due to the radiating fin provided on the upper surface of the heating part and, thus, the cooler is not suitable for a thin type electronic device like a notebook personal computer.
For this reason, in a recent thin type electronic device such as a notebook personal computer, the heat has been radiated out by transferring the heat generated from the heating parts to the body of the device or the keyboard through a heat pipe. In such a type of cooler, when the heat is radiated outwardly, forcible air-cooling by means of a small size fan or the like is carried out in order to enhance the effect for heat-radiation.
However, although the cooler described above using the heat pipe satisfies the requirement for producing a thin type electronic device, the effect of heat-radiation is limited due to the use of the heat pipe, making the cooler unsuitable for an electronic device accommodating an electronic part which generates a large amount of heat such as a CPU having an increasingly improved performance.
As a cooler which has solved such problem and which has an enhanced effect of heat-radiation, a cooler has been suggested in Japanese Patent Laid-Open No.7-142886, in which a cooling liquid is circulated within the heating element to allow the heating element to be forcibly cooled. Such type of conventional cooler will now be described by referring to FIG. 7.
As shown in FIG. 7, a heating element c such as a semiconductor element is provided on the surface of a wiring substrate which is stored in a body made of metal, this body being in the form of a casing of the electronic device. A cooler for the heating element c is composed of a heat-receiving header d provided on the upper surface of the heating element c, a radiating header e secured on a metal casing g in the form of a case lid and a pair of flexible tubes f communicating with the inside of the heat receiving header d and the inside of the radiating header e.
Furthermore, a liquid channel in which a liquid flows back and forth is formed within the heat-receiving header d. Both ends of the liquid channel are connected to the inside of the radiating header e via the two respective flexible tubes f. A liquid channel in which a liquid flows back and forth, a piston for circulating a cooling liquid within the liquid channel and a motor which drives the piston via a link mechanism are placed within the radiating header e.
In the cooler for an electronic device thus constructed, the heat generated from the heating element is transmitted to the heat-receiving header d, and the heat received by the heat-receiving header d is then transmitted to the cooling liquid which flows within the heat-receiving header d.
Almost all of the heat transmitted to the cooling liquid is then transmitted out to the radiating header e from the inner wall of the liquid channel within the radiating header e, but the remaining part of the heat maintains the temperature of the cooling liquid.
The heat transmitted to the heat-radiation header d is mainly emitted to the atmosphere via the metal body g, but if there is heat which is not emitted, the temperature of the heat-radiation header e is kept high.
Technical problems for the cooler for an electronic device described above also remain as described herein below:
(1) There is a technical problem that due to the increases in the much higher processing speed and performance of the CPU and due to the modularization of the components and the onboard new units associated with multimedia accompanying the progress in the CPU, power consumption is rapidly increased to in turn increase the amount of the heat generated from the heating elements contained in the electronic device, so that the heat transmitted to the cooing liquid cannot be sufficiently radiated out through the radiating header. Furthermore, since the circulation of the cooling liquid is carried out by means of the piston, the circulation of the cooling liquid becomes discontinuous, making it impossible to sufficiently radiate out the heat.
(2) Since the heat-receiving header and the radiating header are connected by means of the flexible tubes, there is a risk of damaging the electronic device itself when the flexible tubes are damaged, causing the cooling liquid to leak. What is worse, there is a technical problem with regard to many more man-hours being required for mounting, since in the cooler described above, after the heat-receiving header and the radiating header have been mounted, the flexible tubes must be placed on the wiring substrate.
(3) Moreover, the parts composing the cooler is separately distributed therewithin, making it difficult to cut down on the space in a notebook personal computer or the like. This prevents the notebook personal computer or the like from being downsized and made thinner.
As described above, no cooler has yet been provided which fulfills the following requirements for a smaller size or thinner type of electronic device like a notebook personal computer, i.e., the cooler must be smaller and thinner, the cooler must have an effective and sufficient effect for heat-radiation, and the cooler can safely be used in such an electronic device.
The present invention has been made to solve the technical problems described above, and an object of the present invention is to provide a cooler for an electronic device which is smaller and thinner than the conventional cooler, which can show a sufficient cooling effect with higher effectiveness, and which has no risk of being damaged.
A cooler for an electronic device according to the present invention, which has been made to attain the object described above is a cooler for an electronic device which cools a heating element provided on the electronic device, which comprises: a liquid cooling mechanism composed of a heat sink which is formed in a flat shape, having a heat-receiving face at one surface thereof intended to be in contact with said electronic device, and having a liquid channel accommodated therein, a pump portion comprising a housing which is formed into a flat shape and which has an impeller, which can be rotated, provided therein, and metal pipes, each of which connects said liquid channel to said pump portion; and a forcible air cooling mechanism, composed of a radiating fin provided on the outer surface of said metal pipes, and a fan which cools said radiating fin and said housing, said liquid cooling mechanism and said forcible air cooling mechanism being unified with each other.
Due to such a construction, since the heat sink is formed into a flat shape, the heat-receiving face can be enlarged and, thus, the heat generated in the electronic device is transmitted to the liquid channel via the heat-receiving face having such an enlarged area, making it possible to maintain the temperature of the electronic an device within the tolerance level. On the other hand, since the cooling liquid heated due to the heat exchange is forcibly cooled by means of the forcible air cooling mechanism, the cooler can maintain a large cooling effect, even if the electronic device is used over a prolonged period of time. The higher the cooling effect of the cooler, the easier the downsizing of the cooler becomes.
Since the pipe portion and the liquid channel of the heat sink are connected by means of the metal pipes, there is no risk of leakage of damaging the electronic device itself. What is more, the cooler of the present invention is unified into a whole unit and is made into a fixed form by connecting the pump portion and the heat sink by means of the metal pipes. Consequently, in contrast to the conventional cooler, it is not required to place flexible tubes on the wiring substrate, so it becomes easy to mount the cooler. Moreover, the pump can be continuously driven, making it possible to continuously and effectively cool the cooling liquid.
It is desirable for the cooler of the present invention to arrange the impeller and the fan therewihin such that the axis of the rotation of the impeller forming the forcible air cooling mechanism are positioned on an identical line. In the case where the impeller and the fan are arranged such that the axis of the rotation of the impeller forming the liquid cooling mechanism and the axis of the rotation of the fan forming the forcible air cooling mechanism are positioned on an identical line, the forcible air cooling mechanism can be placed in the vicinity of the pump portion, and this makes it possible to improve the cooing efficiency.
It is also desirable for the fan and the impeller to be rotated at the same time together. More specifically, the fan and the impeller are adapted to rotate together by providing said fan with a magnet for rotating the fan which rotates under the influence of the magnetic fluctuation of a motor substrate and another magnet for driving the impeller while providing said impeller with a passive magnet which receives the magnetic force from said magnet for driving the impeller. It may also be possible to design such that the fan and the impeller are rotated together by providing said fan with a magnet for rotating the fan which rotates under the influence of the magnetic fluctuation of a motor substrate while providing the impeller with a passive magnet to receive the magnetic force from said magnet for rotating the fan.
Thus constructed, the mechanism for driving the fan and the mechanism for driving the impeller can be simplified and, thus, it becomes possible to miniaturize the forcible air cooling mechanism and the pump portion.
Particularly, in the case where the fan is provided with a magnet for rotating the fan which rotates under the influence of the magnetic fluctuation of the motor substrate and a passive magnet which receives the magnetic force from said magnet for rotating the fan, the constructions of the mechanism for driving the fan and of the mechanism for driving the impeller can be simplified much more than the constructions described above.
Desirably, the motor substrate is made of an insulating plate having a coil formed on the surface thereof, the fan is in the form of a thin plate having a plurality of bent blades at the periphery of a thin plate member having a rotation axis at the middle portion thereof while the motor substrate, the fan, and the flat pump portion are laminated on each other.
This construction has a merit in that the pump portion and the forcible air cooling mechanism has a compact and integrated structure.
Furthermore, it is desirable that the metal pipes each connecting the pump portion to the liquid channel of the heat sink are folded at least once at a position between the pump portion and the heat sink, and a radiating fin is placed on the folded portion.
Where the radiating fin is placed on the folded portion, the radiating fin can be tightly fixed onto the portion between the metal pipes and, at the same time, the area in contact with the metal pipes can be enlarged, making it possible to improve the cooling efficiency of the metal pipes.
Furthermore, the radiating fin and the portions of the metal pipes on which the radiating fin is placed are desirably mounted in contact with the mounting plate having thereon a housing provided which forms the pump portion. When the radiating fin and the portions of the metal pipes on which the radiating fin is placed are mounted in contact with the mounting plate having thereon a housing provided thereon which forms the pump portion, the heat is also transmitted to the mounting plate, and it becomes possible to carry out the cooling through the mounting plate.
In the case where a port capable of causing air to pass therethrough is formed on at least one portion of the mounting plate which is positioned on the radiating fin, the air passes by the radiating fin to forcibly cool the radiating fin, which makes it possible to improve the cooling efficiency.
It is desirable from the viewpoints of heat conductivity and prevention of corrosion that the heat sink is made of aluminum which is a highly heat-conductive material, and that the metal pipe is made of copper.